1. Technical Field
The present invention relates generally to protective materials, and in particular, to reactive and adsorptive materials for providing multi-functional protection from chemical and biological agents and methods for providing and using such materials.
2. Description of Related Art
A) Chemical Agents
Agents of chemical warfare have existed for a long time and are generally grouped into the following three classes: 1) blister/percutaneous agents 2) nerve agents, and 3) blood agents.
1) Blister/percutaneous agents attack the skin and/or mucous membrane tissues external or internal to the human body, including the inhalation route. The resulting blistering and ulceration is extremely debilitating and can be fatal. Typical of this class is Mustard (labeled as Agent HD) which can be present as a liquid or a gas, or within an aerosolized carrier.
These agents were found early on to be readily absorbed by activated carbon which, when contained within canister beds or immobilized/fixed within or upon various textile substrates, offered the ready capability to absorb such agents and hold them away from vulnerable body areas of the person to be protected. Activated carbon has been made into and presented as powders, granules, dried slurries, fibers, spherical beads, etc. and is derived from a variety of processes which are performed on organic precursors such as coconut husks, wood, pitch and organic resins. Each process is unique but can be reduced in view to the following steps: (a) carbonizing the organic precursor material to carbon of modest internal surface area (of the order of tens to a few hundred of square meters or surface area per gram of carbon), and then (b) activating this carbon to produce a carbon with many hundreds to low thousands of m2/gm of surface area. Such activated carbon has strong adsorptive abilities. The word adsorb is important here. When a material adsorbs something, it means that it attaches to it by chemical attraction. The huge surface area of activated carbon gives it countless bonding sites. When certain chemicals pass next to the carbon surface they attach to the surface and are trapped.
The carbons worked with must be fixed within or upon a carrier substrate in order to be rendered into a useful form. Such fixation, whether by way of adhesion or entrapment or some other mode of fixing the carbon on the carrier, must be done deftly enough such that as little as possible of the valuable surface area is obfuscated by the fixation process.
2) The nerve agents comprise a variety of compounds which can be presented as gases, liquids or secured either in aerosol or other carriers, much as is HD. They attack the human body and interfere with nervous system functioning via immobilization of key enzymes necessary therein, causing death or severe injury. They all operate principally via percutaneous and inhalation routes and are extremely toxic even in miniscule amounts. Typical of such species are Sarin and Soman, often referred to as the G agents (GB and GD). They are also efficiently absorbed by carbon of high surface area with the same carbon source/process and fixation considerations as discussed above.
3) The blood agents are those species which, when inhaled, dissolve via the lungs in the blood and cause asphyxiation by displacing the oxygen (O2) normally carried by the hemoglobin moieties with more potently binding species known as strong Lewis Bases. Such agents include Hydrogen Cyanide (HCN), Carbon Monoxide (CO), Phosgene (COCl2) and others. The blood agents are minimally and essentially ignorably absorbed by the activated carbon spoken of above. This is because the blood agents constitute molecules of too low a molecular weight such that their fugacity at normal temperatures exceeds any surface bonding power which the activated carbon can offer. Indeed, though activated carbon is good at trapping carbon-based impurities (“organic” chemicals), as well as things like chlorine, many other chemicals (sodium, nitrates, etc.) are not attracted to carbon at all, and therefore pass through unabsorbed. This means that an activated carbon filter will remove certain impurities while ignoring others.
It is to be noted that there are some chemical agents which can arguably be either percutaneous, inhalation or blood agents, or some combination of these simultaneously. However, for the purposes mentioned herein, such species would operationally fall into one or more of the modes of handling which are cited above.
B) Biological Agents
The agents of biological warfare include bacteria, viruses, fungi and spores (which some species generate as dormant “seeds” or genetic progenitors of themselves). The principal difference between biological agents and chemical agents is size; biological agents are larger, typically from one to a few tenths of a micron (1 micron=1 micrometer=1μ=1×10−6 meter) up to multiples of microns for agglomerated colonies of same. Thus, biological agents are typically at least about a thousand times larger than chemical agent species.
All of the biological agents have membranaceous coatings for forming a self-containing protective sack around their vital components. These coatings may range from being lipids to lipoprotein and/or numerous variants thereof. These coatings are all stretched membranes, and the process of rupturing same is called lysis and defines the death of that entity as a biological agent. The contents within the membrane or the excreta of living biological entities can produce toxins which are not biological agents but instead are chemical agents whose molecular sizes are large but definitely within the molecular size category.
An effective mode of biological protection is to cover the person with an impenetrable barrier or “baggie” through which biological and even chemical entities cannot pass. However, human life's requirements of breathing, respiring and maintaining a not unacceptably high core body temperature under workload conditions make this solution unrealistic. Alternatively, the pores of activated carbon cannot absorb biological agents due to their size; they rapidly block the outer pores of carbon particles and deny them any further absorption ability. The use of biocidal materials which emit chemical entities upon/into biological intruders or through chemical and or mechanical contact cause lysis of the agent, is one possible mode of providing protection against biological agents. Such biocidal materials include a form of matter known as nanoparticular matter within which a huge portion of the atoms/ions thereof are at a surface of the particle. Such surface entities are very reactive toward organic chemical and biological entities and are also very small with jagged edges; both these features assist in causing the desired lysis of biological agents.
To fulfill a long standing need to provide biocidal components for protective systems for military and civilian EMS applications, scientists have been developing metal-based nanoparticles. U.S. Pat. No. 6,057,488 discloses effective biocidal properties of metal-oxide nanoparticles when dispersed as a powder or combined in a test tube with biological contaminants. Due to the unique physical properties and size of nanoparticles, it has heretofore been impossible to separate and fix the nanoparticles into a tangible form that could be flexibly integrated into protective systems and combined with conventional adsorbents.
Accordingly, a need exists for materials in a form which is easily handled during use and manufacturing of same which have improved adsorptive properties for more effective adsorption of impurities and which concurrently also have reactive and biocidal properties for adsorption and neutralization of chemical agents as well as destruction of biological agents.